The use of hand trucks, dollies, and step ladders by private individuals and businesses is widely known. Such devices are commonly used for moving, lifting, and supporting loads in the performance of various physical tasks. Accordingly, the need and desirability for such devices is without question, and need not be discussed herein.
Numerous designs have been utilized over the years for individual hand truck, dolly and step ladder devices. In fact, such devices have been combined into a single device, such as the combination hand truck, step ladder, and basket carrier of U.S. Pat. No. 6,173,811, the combined hand truck and ladder of U.S. Pat. No. 4,106,590, the step ladder dolly of U.S. Pat. No. 3,954,155, and the hand truck of U.S. Pat. No. 3,104,889.
However, these combination devices have generally failed in providing the user completely functional embodiments of the respective individual devices. The task of combining multiple functionalities into a single device is inherently difficult to do without sacrificing some of the functionality in exchange for the added convenience of having the combination in a single device. For example, the hand truck of the '889 patent does not have an upright handle in the dolly configuration, only has three wheels in the dolly configuration, and does not provide for the locking of the ladder support or prop in the hand truck configuration. As further examples, the step ladder dolly of the '155 patent does not have an upright handle in the dolly configuration, and the combined hand truck and ladder of the '590 patent requires the device to be inverted from the hand truck configuration in order to configure the device as a step ladder, as shown in FIG. 7 thereof. In addition, the step ladder configuration of the '590 patent is limited in the load that it can support based upon the design of the back frame member, which supports the ladder. As a final example, the combination hand truck, step ladder, and basket carrier of the '811 patent does not include a dolly configuration nor means for locking the hand truck support frame assembly and the step ladder support frame assembly together when in use, such as in the hand truck configuration.
Thus, an unresolved need exists in the industry for a combination hand truck, step ladder and dolly that is fully functional in each configuration and a hinge system that secures the device in certain configurations.